I've a friend, no really, who's wife has forgotten her owner password on their two user account Wallstreet PDQ running OS 9.2.2. We can accesses his account but he has no privileges. I have a disk from which to boot and need to know how to disable the Multi-User functionality, or better yet, reset the password without knowing the current one.

No real way to reset the password through multiple users, however you can boot up off the CD and naviagate to the:
Macintosh HD:System Folder:Extensions:Multi-User (Multiple Users)
* Sorry it's been so long since I have used Mac OS 9)
Anyways find those file(s) and move them only the desktop (or root level of your regular boot drive) and reboot if you'd like to.

If you want to go one step further, you can navigate to:
Macintosh HD:System Folder:Preferences and delete the multi-user preference and you should be able to rebuild the multiple user accounts under Mac OS 9 upon a reboot. It "could" also be a folder called Multiple Users or multi-users.